Why do brood combs turn black?

It doesn’t take long to discover that brood combs can turn dark as night after just one season while honey combs stay light for many years. What causes this difference? Several reasons are usually given for this phenomenon, but in truth, it is probably a combination of all them that causes brood comb to darken so quickly.

The cocoons that remain in the cell after the bees hatch are the major problem. The cocoons are extremely sticky and, try as they might, the bees cannot strip it all from the comb. Some say the darkness is caused by the feces that remains in the bottom of the cocoons. Although this may be partially true, based on what I’ve read, the bees manage to remove most—if not all—of the feces as they prepare the cell for the next generation.

What is more likely is that the sticky cocoons attract all sorts of hive debris, from dirt tracked in on bee feet (many bees times six), pollen grains, and atmospheric dust. In addition, the bees polish the insides of these cells with propolis to make the surface smooth and to take advantage of the many antimicrobial agents found in the propolis.

The color found in the dirt and debris, combined with the layers of propolis—which is usually dark—probably accounts for most of the color change.

But, you say, the inside of honey cells are brushed with propolis too. That is true, but the honey cells do not contain cocoons and they are emptied and polished seldom—usually only once a year. Brood cells, on the other hand, may be polished and reused every 21 or 22 days during the spring and summer—a huge difference.

Another difference between honey comb and brood comb is the amount of bee activity. Once a honey cell is filled the bees move on to another. But once an egg is laid in a brood cell, the uncapped larvae is fed a thousand times a day—quite a different traffic pattern.

The buildup of cocoons and propolis in brood cells is significant. Some researchers have analyzed brood comb and found that the cells become measurably smaller as the walls become thicker. If you render your own beeswax, you know how much more debris is filtered from melted brood comb than melted honey comb. Clumps of this debris, appropriately called “slumgum,” clog strainers and mesh bags, and tiny bits of it darken the liquid wax.

The question always arises whether dark comb is harmful to bees. In truth, bees love dark comb and it is often used in bait hives to attract wild swarms. I’ve heard rumors about beekeepers using black comb for twenty-five years with no ill effects.

Recently, however, there is concern about pesticide build-up in old combs, as well as the accumulation of some pathogens. Many sources now recommend rotating old black comb out of the hive every four or five years, not because of its color but to protect the hive from these pesticides and pathogens.

Rusty
HoneyBeeSuite

The upper part of the comb has never been used for brood and remains light. The lower portion has contained brood and is starting to darken. Flickr photo by Jordan Schwartz.

Comments

Emily
Reply

Here in the UK government bee inspectors recommend changing brood combs at least every three years and preferably all at once using a procedure such as the shook-swarm or Bailey comb exchange. I’ve heard them say that in the wild brood comb will naturally regularly drop off and then be destroyed by wax moths, so that it wouldn’t be hanging around for decades.

Rusty
Reply

That makes sense, Emily. Old comb gets very brittle, so it makes sense it would break off as it aged. So once again, nature takes care of its own. Good insight.

Amanda
Reply

My husband retrieved a beehive from his work that needed to be taken down. Its comb is black; I believe the hive is very old. The hive was located in a area where chemicals are processed. But these same chemicals my husband comes home covered in every day. The honey is dark and good; it is like espresso, very bold. Is it harmful or how can one tell? Thanks for your response Amanda

Rusty
Reply

Amanda,

The honey is probably just fine. Very dark or black comb happens naturally when it is reused by the bees year after year. Sometimes comb can turn dark after only one year. Dark honey is the result of the type of flowers that the bees collected from. In most cases, the darker the color, the richer the flavor. You are lucky to have found this.

Amanda
Reply

I thought so 😉 thanks for the confirmation! I call it blessed!

Bill R
Reply

Hi Rusty,

I just had an online chat with another beekeeper and he was convince that dark comb will darken honey that is stored in it. Now, I haven’t seen this to be true myself. Have you heard of this or know anything about the possibility of honey being color by dark (I presume brood) comb? Now, I know that honey color is dependent on what plant the bees have been working, not the color of the comb, but I am open to learning new stuff.

Thanks,

Bill

Rusty
Reply

Bill,

I have never heard of dark comb darkening the honey. For one thing, bees polish the inside of brood cells before they are reused. Apparently they remove any loose debris and then use a thin coating of propolis and/or beeswax to seal in anything that might contaminate future brood, honey, or pollen.

Neither beeswax nor propolis are water soluble, but honey is. This means that debris that is sealed beneath a layer of wax and or propolis will not get dissolved into the water-based honey. Surely honey in dark comb looks darker while it is still in there, but we’ve all seen water-white honey come out of very nasty-looking comb.

Abdullah
Reply

we had honeycomb in our home after 3-4 years all bees fly away and there is not any bees left and when i cut honey comb it have dark color but there is no honey in there
i want to what it causes that bees flees away and there is no honey in there

Rusty
Reply

Abdullah,

From here I can’t say why your colony disappeared. If there was no honey at all left in their hive, that could be the reason. Maybe there weren’t enough flowers for them to survive. Also, they could have been plagued by predators, parasites, diseases, or lack of water. The dark brood combs are caused by layers of cocoons which the hatching bees leave behind. Dark comb is completely normal.

Ike
Reply

I tried something new this year. I had seen this done several times. Mixing a small amount of wintergreen oil and diluting it way down then mixing in the sugar water feed. This is for mites and hive beetles that won’t tolerate the small amounts of wintergreen. However, 4-6 weeks later we received a cold snap unexpectedly and I placed an entrance reducer at the front of my hives. 3 hives absconded within the following week leaving plenty of honey behind. My theory is that I mixed the wintergreen a little to stout and when I sealed off the entrance way the wintergreen smell was overwhelming causing them to leave. I could taste it in some of the honey….. maybe bees absconding with honey in the hive has a lot to do with what they foraged on and if they were able to dry the nectar before cold weather caused the hive to be too cold from moisture or a combination of these things. Learned a valuable lesson from this… very disappointing.

Rusty
Reply

Ike,

This doesn’t sound right. How much wintergreen did you use? I’ve mixed it in sugar syrup to use as an attractant and the bees love it. You would have to use large quantities, I think, to get them to abscond. And three hives absconding all at once is almost unheard of. And why would they wait 4 to 6 weeks before they left? Seriously, I think something else is going on here. Did you do a mite count? The colonies may have collapsed from Varroa mites.

de
Reply

Would like to reuse plastic frames with dark comb. I doubt there is concern for much in the way of pesticides or other problems. Can I just scrape off the old comb with hive tool, leaving just a thin layer of wax, much like what new plastic frame comes with. Will bees rebuild on this?

Rusty
Reply

de,

Yes, you can scrape it off and the bees will rebuild on it.

de
Reply

Thanks Rusty!!!

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